Division of Genetics, Department of Pediatrics, University of California San Francisco, San Francisco, California, United States of America.
PLoS One. 2010 May 11;5(5):e10565. doi: 10.1371/journal.pone.0010565.
Anophthalmia and microphthalmia are important birth defects, but their pathogenesis remains incompletely understood. We studied a patient with severe unilateral microphthalmia who had a 2.7 Mb deletion at chromosome 18q22.1 that was inherited from his mother. In-situ hybridization showed that one of the deleted genes, TMX3, was expressed in the retinal neuroepithelium and lens epithelium in the developing murine eye. We re-sequenced TMX3 in 162 patients with anophthalmia or microphthalmia, and found two missense substitutions in unrelated patients: c.116G>A, predicting p.Arg39Gln, in a male with unilateral microphthalmia and retinal coloboma, and c.322G>A, predicting p.Asp108Asn, in a female with unilateral microphthalmia and severe micrognathia. We used two antisense morpholinos targeted against the zebrafish TMX3 orthologue, zgc:110025, to examine the effects of reduced gene expression in eye development. We noted that the morphant larvae resulting from both morpholinos had significantly smaller eye sizes and reduced labeling with islet-1 antibody directed against retinal ganglion cells at 2 days post fertilization. Co-injection of human wild type TMX3 mRNA rescued the small eye phenotype obtained with both morpholinos, whereas co-injection of human TMX3(p.Arg39Gln) mutant mRNA, analogous to the mutation in the patient with microphthalmia and coloboma, did not rescue the small eye phenotype. Our results show that haploinsufficiency for TMX3 results in a small eye phenotype and represents a novel genetic cause of microphthalmia and coloboma. Future experiments to determine if other thioredoxins are important in eye morphogenesis and to clarify the mechanism of function of TMX3 in eye development are warranted.
先天性无眼症和小眼球症是重要的出生缺陷，但它们的发病机制仍不完全清楚。我们研究了一位患有严重单侧小眼球症的患者，他从母亲那里遗传了一条 18q22.1 染色体上的 2.7 Mb 缺失。原位杂交显示，缺失的基因之一 TMX3 在发育中的鼠眼视网膜神经上皮和晶状体上皮中表达。我们在 162 名先天性无眼症或小眼球症患者中重新测序了 TMX3，发现了两个无关联患者中的错义替换：c.116G>A，预测 p.Arg39Gln，在单侧小眼球症合并视网膜裂孔的男性患者中，以及 c.322G>A，预测 p.Asp108Asn，在单侧小眼球症合并严重小颌畸形的女性患者中。我们使用两种针对斑马鱼 TMX3 同源物 zgc:110025 的反义形态发生素进行研究，以检查在眼睛发育过程中降低基因表达的影响。我们注意到，两种形态发生素产生的突变体幼虫的眼睛尺寸明显较小，并且在用针对视网膜神经节细胞的胰岛-1 抗体进行标记时，在受精后 2 天减少。共注射人类野生型 TMX3 mRNA 可挽救两种形态发生素获得的小眼表型，而共注射人类 TMX3(p.Arg39Gln)突变型 mRNA，类似于小眼球症和视网膜裂孔患者的突变，不能挽救小眼表型。我们的结果表明，TMX3 的单倍不足导致小眼表型，代表了小眼球症和视网膜裂孔的一种新的遗传原因。未来的实验需要确定其他硫氧还蛋白是否对眼睛形态发生很重要，并阐明 TMX3 在眼睛发育中的功能机制。
